1. Field of the Invention
The present invention relates to a method for surface treatment of a group III nitride crystal that is suitably used, for example, as a material for a substrate of a semiconductor device.
2. Description of the Background Art
The surface of a grown group III nitride crystal to be used for example as a material for a substrate of a semiconductor device is preferably treated so that the surface is as flat as possible and as low as possible in impurity concentration. U.S. Pat. No. 6,399,500 accordingly discloses that the surface of a Ga1-X-YAlXInYN crystal is polished with a basic polishing solution that does not contain abrasive grains and thereafter polished with pure water.
The group III nitride crystal, however, is chemically stable and thus the polishing efficiency is still low when polished with the basic polishing solution without containing abrasive grains as described above.